Selective Photoinduced Oxidation of Benzylic Methylen Groups through UV Irradiation in Presence of Ferric Chloride

Article abstract of DOI:10.1002/hlca.19840670327

Selective oxidation of benzylic methylene groups through UV irradiation in acetone/water/FeCl3 mixtures is reported.This method applied to a series of model compounds, provides an easy access to the corresponding 1-oxo derivative.Thus, tetralin gives a 100percent yield of 1-tetralone, indane leads to 60percent of 1-indanone, and diphenylmethane is oxidized to benzophenone with 80percent yield.However, under the same conditions, alkyl-substituted aromatic hydrocarbons such as toluene, ethyl- and propylbenzene lead to low yields of aldehydes or ketones.Isochromane furnishes a mixture of two substances which can be interconverted, namely the expected 1-isochromanone (9percent) and the corresponding hydroxy acid (23percent).We failed to apply the method to nitrogen heterocycles containing benzylic groups such as 1,2,3,4- and 5,6,7,8-tetrahydroquinoline as they do not react due to the formation of complexes which precipitate from the solutions.